Drivers are commonly used in a wide variety of applications to output signals to electrical components. Drivers may, for example, be used as an interface between circuits of varying voltage levels. Drivers are also often used for signal outputs in single power supply systems. In complimentary metal oxide semiconductor (CMOS) devices; a typical driver includes a predriver coupled to two signal drivers or output devices. One single driver device is typically a p-channel field effect transistor (PFET) or pull-up transistor and the other typically is an n-channel field effect transistor (NFET) or pull-down transistor. An exemplary driver is shown in Nguyen et al., U.S. Pat. No. 5,467,031, the contents of which are herein incorporated by reference.
Two of the more important performance characteristics of a driver circuit are switching speed and noise. Both of these performance characteristics are dependent upon the current slew rate, i.e., the change in current over time (di/dt) through the signal drivers. In particular, the switching speed of a signal driver is generally determined by the minimum current slew rate which is needed to turn-on the signal driver, while noise is dependent upon the maximum current slew rate through the transistor. The current slew rate through signal drivers however varies with variations in the temperature, voltage, and processes to which the signal drivers are subjected. These variations in the signal driver current slew rate limit the speed of present signal drivers as well as the number of signal drivers that can be provided on a given chip or chip set.